Please actually link to the stuff you're talking about? I take it is
this. I think the rostock design also saves on one stepper.(magnitude matters; ~15$ to ~20$ i think) It has longer belts though, dont think that adds much in the price.
They call themselves 'pirates' but follow the main stream in their style of main presentation. They do say they'll release designs of their future boards and software as open source though.(Hope they keep their word)